AB1554 A STUDY TO SHOW THE TOLERABILITY OF ULTRASOUND GUIDED SIJ STEROID INJECTION TO ALLOW APPROVAL OF US GUIDED SIJ SYNOVIAL TISSUE SAMPLING FOR RESEARCH
Authors: J. Bunting, A. Tan, N. Purkayastha
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Sacroiliac joint (SIJ) synovial tissue analysis has the potential to improve specificity and sensitivity of spondyloarthritis (SpA) classification beyond the current Assessment for SpondyloArthritis International Society criteria allowing early diagnosis and reducing disease progression. It can aid the use of molecular biomarkers and identification of drug targets already explored in rheumatoid arthritis (RA) [1]. Furthermore, joint synovial tissue has shown histological differences in RA from psoriatic arthritis [2] and may help characterise SpA subtypes. SIJ steroid injections are used for pain management. A similar procedure, yet to be utilised, can be used to obtain synovial tissue using a co-axial needle. There is evidence of histological disease in patients experiencing sacroiliac pain without MRI features [3, 4]. Synovial biopsy offers possible earlier detection of SpA than MRI, which is limited by cost, patient weight and claustrophobia. Equally fluoroscopic or CT guided injections are limited by cost, time and radiation exposure. Early diagnosis and treatment of SpA is already linked to improved outcomes [5]. <h3>Objectives</h3> To determine the tolerability and safety of ultrasound guided (USG) SIJ steroid injections to encourage SIJ tissue biopsies in research. <h3>Methods</h3> We identified 10 patients at Southend Hospital between 2010-2019. The average age was 41 years. Once verbal consent was obtained, a retrospective telephone questionnaire was completed. The USG SIJ steroid injections (Figure 1A) involved injecting Lidocaine 1% around the soft tissue using a 25G and 23G needle. Then a 22G spinal needle was guided into the SIJ and a mixture of Depomedrone 40mg and 0.5ml 0.25% bupivacaine administered. The patients were asked to indicate pain, swelling and stiffness of the injected joint pre and post procedure using a qualitative scale: none, mild, moderate or severe. They were asked to comment on side effects and how likely they were to repeat the procedure. <h3>Results</h3> All patients had severe pain before injection and one continued to have severe pain post procedure. None reported complications of steroid flare or back pain (Figure 1B and 1C). 70% experienced temporary numbness (Figure 1B), an expected side effect of local anaesthesia, which resolved within 24 hours. No permanent numbness was reported. 20% had peripheral arthralgia, which resolved with analgesia in 24 hours. 50% were unlikely to repeat the procedure as the steroid offered little benefit. Most importantly, all patients tolerated the procedure with only mild to moderate discomfort. <h3>Conclusion</h3> SIJ steroid injections are not widely offered, making it difficult to obtain large patient numbers. However, this study shows that SIJ steroid injections are tolerable for patients, an important step in convincing patients to participate in a SIJ synovial tissue biopsy research study. Tissue biopsy using a co-axial needle may be considered more invasive as it is thicker with a longer throw than a 22G spinal needle but the procedure steps and complication risks are ultimately similar. The complication risk rate has not yet be compared between the two procedures but SIJ tissue biopsy is less invasive and traumatic than the alternative SIJ trans-articular bone biopsy [6]. Whilst sample size may not be representative for a larger patient cohort and the retrospective questionnaire may have introduced time bias, the data obtained will hopefully initiate a potential study. This study could provide significant information on complication risk rate in synovial tissue biopsy of the SIJ and associated histological disease information in SpA. <h3>References</h3> [1]Humby F et al. Lancet 2021 [2]Veale DJ et al. RMD open 2015 [3]Gong Y et al. Arthritis Rheum 2012 [4]Bollow M et al. ARD 2000 [5]Sieper J et al. ARD 2005 [6]Egund N et al. Skeletal Radiol 2020 <h3>Acknowledgements</h3> We would like to acknowledge our coding team at Southend Hospital and Consultant Radiologist, Dr Perera for providing the patient list. <h3>Disclosure of Interests</h3> Jessica Bunting: None declared, Alan Tan: None declared, Nirupam Purkayastha Shareholder of: Sareum Holdings, Consultant of: Galapagos.